49 CFR 179.4 - Changes in specifications for tank cars.
(a) Proposed changes in or additions to specifications for tanks must be submitted to the Executive Director - Tank Car Safety, AAR, for consideration by its Tank Car Committee. An application for construction of tanks to any new specification may be submitted with proposed specification. Construction should not be started until the specification has been approved or a special permit has been issued. When proposing a new specification, the applicant shall furnish information to justify a new specification. This data should include the properties of the lading and the method of loading and unloading.
(b) The Tank Car Committee will review the proposed specifications at its earliest convenience and report its recommendations through the Executive Director - Tank Car Safety to the Department. The recommendation will be considered by the Department in determining appropriate action.